1. Field of the Invention
This invention relates to techniques for tracking a spinning projectile or missile and determining its instantaneous attitude while in flight.
2. Description of the Related Art
The purpose of this invention is to provide instantaneous attitude measurements for spinning command-guided projectiles such as gun-fired projectiles, EKVs and certain classes of tactical missiles. Such projectiles can be very low cost, since they do not require seekers or complex on-board computers for processing seeker information or GPS receivers and on-board computers. Furthermore, a spinning projectile needs only a single deflection thruster to maneuver in any direction and correct the attitude of the missile since the thruster can be fired at any appropriate roll angle. In operation, a projectile is launched and tracked during flight toward a predesignated target. When it is determined that accumulating errors will cause a miss, a single-shot thruster may be fired late in the flight to correct the trajectory errors. Alternately, canards may be deployed to correct for either crossrange or downrange trajectory errors. These command guided projectiles are much less expensive then either the seeker-guided or GPS-guided systems.
Generally, an on-board inertial measurement unit (IMU) is employed in seeker, GPS and command guided systems to measure attitude; yaw, pitch and roll. IMUs typically consist of three gyroscopes to detect rotation about three mutually orthogonal axes, as well as accelerometers to detect acceleration upon three mutually independent axes. IMUs are expensive, currently ranging from $5,000 to $10,000 per projectile and are not able to survive acceleration in excess of 12,000 g's. This price point is too high for the less expensive gun-fired munitions. Furthermore, next generation systems will generate in excess of 12,000 g's as the range of the weapons continues to increase.
There remains a need for an inexpensive system that is capable of replacing IMUs for command guided weapons systems.